swarm ui: a stored claude login closes the dialog and shows a toast

The login dialog stayed open with a success line after the code was
accepted, though nothing is left to do in it. It now closes and a toast
says the login is stored. The toast is a new swarm-ui primitive: a short
note raised with showToast, rendered by a ToastHost at the app root, gone
after a few seconds or on click.

frontend/packages/swarm-ui/test/claude-login.test.mjs

@@ -12,6 +12,7 @@ import {
   leavesLoginRunning,
   pastedCode,
   startOutlivedDialog,
+  storedMessage,
 } from "../src/agent/claude-login/ClaudeLoginSteps.ts";
 
 test("the routes name the agent, escaped", () => {
@@ -77,3 +78,7 @@ test("a pasted code is trimmed, and a blank one is nothing", () => {
   assert.equal(pastedCode("  abc-def \n"), "abc-def");
   assert.equal(pastedCode(" \n "), null);
 });
+
+test("the stored toast names the agent", () => {
+  assert.match(storedMessage("atlas"), /^Login stored\. atlas /);
+});

frontend/packages/swarm-ui/test/toasts.test.mjs

@@ -0,0 +1,46 @@
+// The toast list. Run by `npm test`, which Node runs with its built-in test
+// runner and type stripping, so the `.ts` module is imported as it is.
+import assert from "node:assert/strict";
+import { test } from "node:test";
+import {
+  currentToasts,
+  dismissToast,
+  showToast,
+  subscribeToasts,
+  toastDuration,
+} from "../src/ui/toast/toasts.ts";
+
+test("an error stays longer than the other tones", () => {
+  assert.ok(toastDuration("error") > toastDuration("ok"));
+  assert.equal(toastDuration("info"), toastDuration("ok"));
+});
+
+test("a toast is listed with its tone and duration, oldest first", () => {
+  const a = showToast("first", "ok");
+  const b = showToast("second", "error", 100);
+  const list = currentToasts().filter((t) => t.id === a || t.id === b);
+  assert.deepEqual(
+    list.map((t) => [t.message, t.tone, t.duration]),
+    [
+      ["first", "ok", toastDuration("ok")],
+      ["second", "error", 100],
+    ],
+  );
+  dismissToast(a);
+  dismissToast(b);
+});
+
+test("dismissing removes one toast and tells the subscribers once", () => {
+  const a = showToast("keep");
+  const b = showToast("drop");
+  let calls = 0;
+  const stop = subscribeToasts(() => calls++);
+  dismissToast(b);
+  dismissToast(b);
+  assert.equal(calls, 1);
+  assert.ok(currentToasts().some((t) => t.id === a));
+  assert.ok(!currentToasts().some((t) => t.id === b));
+  stop();
+  dismissToast(a);
+  assert.equal(calls, 1);
+});